An internal combustion engine typically includes a combustion chamber, where a fuel air mixture is burned to cause movement of a set of reciprocating pistons, and a crankcase, which contains the crankshaft driven by the pistons. During operation, it is normal for the engine to experience “blowby,” wherein combustion gases leak past the pistons from the combustion chamber and into the crankcase. These combustion or blowby gases contain moisture, acids and other undesired byproducts of the combustion process.
Accordingly, a Positive Crankcase Ventilation (PCV) system is used to remove these harmful gases from the engine and prevent those gases from being expelled into the atmosphere. The PCV system does this by using manifold vacuum to draw vapors from the crankcase into the intake manifold. Vapor is then carried with the fuel/air mixture into an intake manifold of the combustion chambers where it is burned. Generally, the flow or circulation within the system is controlled by the PCV valve, which acts as both a crankcase ventilation system and as a pollution control device. Even with a PCV system, blowby gas may still collect within the engine cavity and further deteriorate ventilation, especially when the engine is running wide open throttle. When the engine is operating at wide open throttle, the manifold pressure is at the same level of engine crankcase and therefore, an additional passage would allow for otherwise built up blowby gas to escape. The operation of a turbocharger in a turbocharged engine is similar to that of an engine running wide open throttle. Therefore, the concentration of blowby gas in the engine head is relatively high. It remains desirable to provide an improved PCV valve design for use in turbocharged engine PCV systems.